Two presidents have been impeached – President Andrew Johnson in 1868 and President Bill Clinton in 1998.
Senators called for President Jackson’s impeachment after he replaced the Secretary of War without Senate approval. The U.S. Senate began proceedings, but votes fell short of the 2/3 majority needed for conviction.
President Clinton was impeached by the House of Representatives on two charges – one of perjury and one of obstruction of justice. Similar to Jackson, once it got to the U.S. Senate, they were unable to convict him without a 2/3 majority.